This invention relates to torque wrenches and more particularly to such wrenches incorporating reaction members for engagement with a fixed component during the tightening or untightening procedure.
When torque tightening a nut or a bolt of a series of nuts and bolts using a torque wrench provided with a reaction member, whether an arm or a foot, the wrench can usually be positioned whereby the reaction member reacts from the nut or bolt to either side of the one being tightened--i.e. the wrench can be located either behind or in front of the row of nuts and bolts.
In certain circumstances, however, there may be restricted access either behind or in front of the row of nuts and bolts whereby a torque wrench can only be located in front of or behind said row. Such a situation can arise, for example, when attaching or removing the individual blades of a ship's propeller to the central hub, and when dealing with the individual blades of a turbine.
Thus it will be appreciated that, when the last bolt in a line of bolts is reached, there is no reaction point available to the torque wrench.
Attempts have been made to overcome this problem of restricted access by providing a torque wrench incorporating a pair of driving heads adapted to tighten two bolts simultaneously, each bolt being tightened also being reacted upon.
However, such a tool has a number of disadvantages. It is a complex, expensive piece of equipment that is dedicated to a particular use and cannot be used for tightening individual bolts. It cannot be used for an uneven number of bolts, while the actual load applied to a bolt may vary in each bolt being tightened, as maximum torque is applied to the tightest bolt. Further, such a wrench cannot cater for differing bolt pitches because of the fixed nature of the driving heads.